Radio remote-control system



July 4, 1950 c. J. MARSHALL RADIO REMOTE CONTROL SYSTEM Filed Aug. 28, 1945 Patented July '4, 1950 unirse s l. FF i Q RADIO REMOTE-CONTROL SYSTEM Charles J. Marshall, Dayton, Ohio, assigner to the United States of America as represented by the Secretary ofthe Army 2 Claims.

amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without lthe payment to me of any royalty thereon.

This invention relates to communication systems and more particularly to communication systems designed to control the operation of a device at a remote point.

It is often desirable to control the operation of several circuits at remote points from one single point. One example of this might be a method of bombing in which several bombing planes flying in a predetermined formation release their bombs simultaneously when the release button is operated in the lead plane. It is obvious that the remote control system for releasing the bombs must be light in Weight since at least the receiving portion of the system must be carried in each of the bombing planes except the lead plane and the lead plane must carry the transmitting equipment for the system. The remote control system must also possess a high degree of reliability for if the system fails to drop the bombs at the proper time a second bombing run must be made over the target or the bombs may have to be jettisoned if a second bombing run is not practical. On the other hand, the system must possess a high degree of security, otherwise spurious signals from either friendly or enemy sources might cause the bombs to drop on friendly targets and thus cause great damage.

It is an object of the present invention, thereforegto provide a simple, novel system for controlling the operation of a plurality of devices at remote points from a single control point. A second object is to make the above remote control system as light, dependable and secure as possible. v c

A third object of this invention is to provide a remote control system that makes the maximum use of radio equipment presently employed in aircraft.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a block diagram of the invention;

Fig. 2 is a schematic wiring diagram of a portion of the receiving system; and i Fig. 3 is a schematic wiring diagram of a-portio of the transmitting system.

Referring now more particularly to Fig. l, there is shown a radio frequency transmitter Il) connected to an antenna I2. Transmitter I may be of a type normally employed for voice coinmunication, or it may be a specially designed transmitter, as it will be explained later. Assuming that it is a conventional communication transmitter, it should be operated on a channel or carrier frequency that is not in use by any other radio transmitters in the vicinity. A signal generator I4 and a signal generator I6 each produce an alternating voltage signal of a predetermined fixed frequency. The two signals from generators Id and I6 respectively are mixed in an electronic mixer circuit I8. and are supplied to the input connection 2E! of transmitter I2 through a switch 22. In the case of a conventional communication transmitter, input connection 20 might be the jacl; provided for connecting a microphone to the transmitter for voice communication. The apparatus just described conn stitutes the entire transmitter component of the remote control system.

The receiving component of the remote control system consists of a radio. receiver 26 with its associated antenna 2B. If transmitter l@ is a conventional communications transmitter, then receiver 2B may be the receiver normally employed to receive the signals from transmitter Ill. The outputv lead Si) from receiver 26 is connected to each of three band-.pass lters 32, 3d and 3,6. Signal output lead 3i) may comprise the signal output jack provided for connecting a conventional headset to receiver 2E. Band-pass filter .'52 is designed to pass a narrow band of frequencies centered about the frequency of the signal produced by generator It While filter 3E is designed to pass a band of frequencies centered about the frequency of the signal produced by generator I6. Filter 34 is designed to pass a narrow band of frequencies intermediate the frequencies passed by lters 32 and 36. The output of lter 32 is connected through an amplifier 38 to the coil of a relay it. Contacts t2 on relay All are normally open but are closed when the coil of relay 4I) is energized. In a similar manner the output of filter 36 is connected through amplifier 4l! to a relay 43. Contacts i8 on relay it are also normally open but are closed when the coil of relay d6 is energized. A third such connection is made from the output of lter 3d through amplifier 5!) to the coil of a relay 52. .ln this case, however, the contacts 5t on relay 52 are normally closed but are opened when the coil of relay 52 is energized. Contacts 42, llt and 54 are connected in series between terminals 55 and 53 of a work circuit 6I). Work circuit 60 is the circuit, for example the bomb release mechanism, that is controlled by the operation of the relay contacts.

The operation of the system is thought to be evident from the above description of the apparatus, but an example is given to illustrate more clearly its operation. Assume that a 30G-cycle signal is generated by generator I4 and a 3000- cycle signal is produced by generator I6. With switch 22 open, only the normal carrier frequency will be radiated by antenna I2. The output of receiver 26 is therefore only the small amount of noise usually found in the output of communication receivers. This noise is not of sufficient amplitude to cause an appreciable signal to be passed 'by any of the band-pass lters. switch 22 closed, however, the signal transmitted With from antenna I2 is modulated with both 300 and 3000 cycles and signals of these two frequencies will appear at output jack 30 of receiverl 26. The 300-cycle-per-second signal passes through filter 32 and amplilier 38 and energizes the coil of relay 40. This causes contacts 42 to close. In a similar manner the 300D-cycle signal energizes the coil of relay 46 causing contacts 48 to close. No signal is present at the output jack 30 that will pass through filter 34; therefore, relay 52 remains deenergized and contacts 54 remain closed. The circuit between terminals 56 and 58 of circuit 60 is now complete, so circuit 60 Will now perform the desired operation. Suppose now that switch 22 is open but that some random signal, for example voice or noise modulations having the same carrier frequency to which receiver 26 is tuned, is being picked up by antenna 28. The random signal in most instances will contain signals of 300 and 3000 cycles of sufiicient amplitude to cause the energization of relays 40 and 40. This random signal will also contain signals that will be passed by iilter 34v of sufficient amplitude to energize relay 52. It can be seen, therefore, that a random signal vwill close contacts 42 and 48, but will open contacts 54 and therefore will not cause circuit G0 to respond to a random signal.

It will be obvious to those familiar with radio theory that the signals produced by generators I4 and I6 may have any Value whatsoever provided transmitter ID and receiver are designed to handle signals of the selected frequencies. It may be desirable to place a detector'after amplifiers 38, 50 and 44 and replace relays 40, 52 and 46 with direct-current relays if the control frequencies produced by generators I4 and I6 are much above 5000 cycles. In other cases it may be desirable to eliminate ampliers 38, 44 and 50 if the output of receiver 26 is of suflicient amplitude to operate relays 42, 48 and 54 directly.

Fig. 2 illustrates a further modification that may desirably be incorporated at times. Contacts 42, 48 and 54 and terminals 56 and 58 correspond to similarly numbered elements in Fig. 1. Switch 62 is added to provide means for manually operating circuit 60 at the remote point. It can be seen that closing switch 62 will have the same effect as closing contacts 42 and 48.

Fig. 3 illustrates a method whereby switch 22 at the control -station is mechanically coupled to a switch 64 corresponding to switch 62, Fig. 2, so that a work circuit at the control point as well as one or more work circuits at remote points will be activated when switch 22 is closed.

While there has been described what is at present considered the preferred embodiment of asias@ the invention, it will be obvious to those skilled in the art that various changes and modications may be made therein without departing from the invention.

What is claimed is:

1. A remote control system including a transmitting component and a receiving component, said transmitting component comprising a iirst signal generator, a second signal generator, an electronic mixer for combining the signals produced by said rst and second generators, a radio transmitter, and means including a switch for connecting said mixer to said radio transmitter, said receiving component comprising a receiver, first, second and third bandpass filters, said rst and third filters being designed to pass signals having the same frequency as signals from said rst and said second signal generators respectively, means for connecting the output of said receiver to each of said lters, iirst, second and third amplifiers for ainplifying the signals passed by said first, second and third filters respectively, iirst, second and third relays responsive to the output of said first, second and thirdampliiiers respectively, means for connecting the contacts of said three relays in a series combination whereby a circuit is co1npleted when said rst and third relays only are energized and no circuit is completed when any other combination of relays is energized, and means for manually completing the circuit normally completed when said first and third relays are energized.

2. A remote control system comprising a trans-v mitter having a rst and a second signal generator, means for combining the outputs of said generators, a receiver having iirst, second, and third filters, said first and third lters being vdesigned to pass signals having the same frequency as signals from said first and second signal generators respectively, said second filter being broadly tuned to the frequencies intermediate to the frequencies of said signal generators, first, second, and third relay means responsive to the outputs of said first, second, and third filters respectively, the contacts of said first and third relays being normally open and that of said second relay being normally closed, and means for connecting the contacts of said relay means in a series combination whereby a circuit is completed when only said first and third relay means are energized and no circuit is completed when any other combination of relay means is energized. l CHARLES J. MARSHALL. Y

REFERENCES CITED The following references are of record in' the file of this patent:

UNITED sTATEs PATENTS Number Name Date` y 1,711,651 Pruden May 7, 1929 1,752,303 Kelley Apr. 1, 1930 1,752,325 Branson Apr. 1, 1930 1,752,346 Kelley et al Apr. 1, 1930 1,984,379 Mirick Dec. 18, 1934 2,148,578 Pullis Feb. 28, 1939 2,155,821 Goldsmith Apr. 25, 1939 2,319,339 Muller et al May 18, 1943 2,401,333 Bumstead June 4, 1946 

